Environmental significance

Statutory EQSs have been set in legislation by the European Commission (EC) and in the UK by the Department of Environment (DoE). Other non-statutory operational standards have been developed by the NRA to control discharges and assess water quality. 

Although statutory standards for List II substances have yet to be set in UK legislation, the Government Advice note Circular 7/89 sets out EQSs for a number of List II substances which are being applied as if they were statutory. Cyfluthrin and permethrin have agricultural approvals, but their detection in the environment is mainly associated with discharges from the moth-proofing industry. 

In addition, the DoE proposed EQSs in a 1991 consultation document for those pesticides on the Red List (the UK s original priority hazardous substances list). Although non-statutory, the Government is committed to the reduction of Red List Substances discharging to the North Sea and the NRA uses the standards to assess the effects of these substances on the environment and to derive consents for point source discharges of these compounds. Failures for agricultural pesticides are rare. 

It is interesting to note that many of the agricultural pesticides exceed 0.1 /tg D S but very few have been recorded as failing these operational standards. In 1993 there were no failures in environmental waters for isoproturon, chlorotoluron, mecoprop or MCPA. 

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Selected Examples of Organic Compounds of Biochemical, Pharmaceutical, and Environmental Significance That Show Natural Fluorescence or t Phosphorescence... 

Rudzinski, W. E. Beu, S. Gas Ghromatographic Determination of Environmentally Significant Pesticides, ... 

EPA has compiled significant data on values of k and n for environmentally significant pollutants with typical activated carbons. Assuming equilibrium is reached, the isotherm provides the dose of carbon required for treatment. In a concurrent contacting process, the capacity is set by the required effluent concentration. In a countercurrent process, the capacity of the carbon is set by the untreated waste pollutant concentration. Thus countercurrent contacting is preferrea... 

Improved targeting of pesticide monitoring will require the development of new analytical techniques and EQSs for priority pesticides to determine their environmental significance. To ensure confidence in the monitoring data, analytical techniques need to be able to detect the pesticide at 1/lOth of the EQS, which can be as low as 1 ngPk... 

Fig. 15-14 Examples of characteristic times for lake transport processes and reactions, and extent of reaction of several environmentally significant reactions in a system with Tphys = 1 day.

There are several environmentally significant mercury species. In the lithosphere, mercury is present primarily in the +II oxidation state as the very insoluble mineral cirmabar (HgS), as a minor constituent in other sulfide ores, bound to the surfaces of other minerals such as oxides, or bound to organic matter. In soil, biological reduction apparently is primarily responsible for the formation of mercury metal, which can then be volatilized. Metallic mercury is also thought to be the primary form emitted in high-temperature industrial processes. The insolubility of cinnabar probably limits the direct mobilization of mercury where this mineral occurs, but oxidation of the sulfide in oxygenated water can allow mercury to become available and participate in other reactions, including bacterial transformations. 

Antoine SR, DeLeon IR, O Dell-Smith RM. 1986. Environmentally significant volatile organic pollutants in human blood. Bull Environ Contam Toxicol 36 364-371. 

Cyclic nitrosamines are among the most potent and environmentally significant nitrosamine carcinogens. Like the acyclic nitrosamines, metabolism is necessary for their carcinogenicity. Elucidation of the specific metabolic pathways of cyclic nitrosamine activation and detoxification is a challenging problem, and considerable progress has been achieved in recent years. In this chapter, we will review metabolic studies on N-nitrosopyrrolidine (NPYR), N -nitrosonornicotine (NNN), N-nitrosopiperidine (NPIP), N-nitrosohexamethyleneimine (NHEX), N-nitrosomorpholine (NMOR),... 

Nitrite (or compounds at the same or lower oxidation level) is produced microbiologically from nitrate, and may then react with the substrate to produce stable end products. The production of nitrite is the sole metabolic function of the bacteria and, in view of concern over the presence of nitrate in groundwater, the following possible environmental significance of these or analogous reactions should not be overlooked ... 

In later chapters, considerable weight is given to the environmental significance of biotransformation and the synthesis of toxic metabolites. It is particularly desirable, therefore, to direct effort to the identification of such metabolites. This may present a substantially greater challenge than that of quantifying the original substrate for several reasons ... 

Coulter C, JTG Hamilton, WC McRoberts, L Kulakov, MJ Larkin, DB Harper (1999) Halomethane bisulfite/halide ion methyltransferase, an unusual corrinoid enzyme of environmental significance isolated from an aerobic methylotroph using chloromethane as the sole carbon source. Appl Environ Microbiol 65 4301-4312. 

Article 4 of Council Directive 91/414 EEC requests Member States to ensure that a plant protection product is not authorized unless its residues, resulting from authorized uses, which are of toxicological or environmental significance, can be determined... 

The results presented here indicate the existence of environmentally significant allelopathic substance or substances that affect a red tide organism in laboratory studies. It would be difficult to imagine that such substances do not have some impact in the natural environment, particularly in view of the observed (26) distribution of aponin vis-a-vis the presence of "seed beds" of red tide (8). 

The cytolytic agent termed aponin has been characterized in terms of biological activity, and the results to date indicate a material that does not adversely affect the organisms tested. Material isolated from cultures of Nannochloris sp. also has some phytotoxic activity as evidenced by the assays with lettuce seeds, and some antifungal activity. The materials elaborated by Nannochloris sp. thus have environmental significance, but it must be admitted that the full significance of these materials, like others, remains to be fully appreciated. 

Suarez, P. and Reyes, R., Heavy metal incorporation in bacteria and its environmental significance, Interciencia, 27 (4), 160-164, 2002. 

This chapter describes some examples of application of alternative methods for the study and characterization of the toxicity of some compounds of environmental significance. 

Mercuric carboxylates, which decarboxylate by a chain mechanism when initiated by peroxides, also decarboxylate under UV irradiation (123,128,129,131-140,142,144-146,153-155). In addition, decarboxylation was observed for mercuric benzoate and mercuric a-naphthoate (123). Side reactions [Eqs. (24), (25), (109)] observed in peroxide initiated reactions also occurred on UV irradiation, and mercurous salt formation [Eq.(24)] was more extensive under the latter conditions. Decarboxylation giving methylmercuric acetate occurred on irradiation of mercuric acetate in aqueous solution and is considered to be of environmental significance (156,157). Stepwise decarboxylation giving (CF3)2Hg occurred on irradiation of solid mercuric trifluoroacetate at -196° C (158), but, at 20° C, trifluoromethyl radicals diffused from the solid and dimerized (158). No other diorganomercurial has been formed by radical decarboxylation, and the reaction is not preparatively competitive with the thermal decarboxylation synthesis of (CF3)2Hg (26,27) (Section III,A). 

Delle Site, A. (1997) The vapor pressure of environmentally significant organic chemicals A review of methods and data at ambient temperature. J. Phys. Chem. Ref. Data 26, 157-193. 

Disproportionation reactions are well known in tin chemistry and can account for the occurrence of several methyltin compounds, assuming a methyltin species was present in the first place. Similarly, transmethylation can occur between inorganic tin species and methylated forms of other elements. Examples of this nature, some of which may take place in water, are given in Section V, Reference 2. Their environmental significance is unknown. Disproportionation reactions are also covered in Section V, Reference 1. A general theory of methylation by MeCoBn was proposed, based on redox potentials51. 

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